Felt with seam for paper manufacture

ABSTRACT

In a seam felt for paper manufacture, seam loops formed at opposite ends of a length of ground fabric to which layers of batt fiber are integrated by needle punching, are formed as groups of loops composed of machine direction yarns. When the opposite ends of the ground fabric are brought together, the groups of loops are intermeshed in an alternating arrangement to form a common bore for receiving a seam thread by which the intermeshed groups of loops are secured together. The loops of each group can be held together by adhesive bonding, or by heat adhesion if the machine direction yarns are core-in-sheath composite fibers wherein the sheath has a lower melting point than that of the core.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority on the basis of Japanese patentapplication 232191/2008, filed Sep. 10, 2008. The disclosure of Japaneseapplication 232191/2008 is hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to a felt employed in the press part of a papermanufacture machine, and particularly to a felt having seam loops,hereinafter sometimes be referred to simply as a “seam felt”.

BACKGROUND OF THE INVENTION

In a paper manufacturing process, water is conventionally squeezed outfrom a wet paper web in the press part of a papermaking machine by meansof a needle felt and a pair of press rolls. It is known to utilize afelt formed into an endless belt by connecting both ends of an elongatedfelt by means of seam loop. As shown in FIG. 1, the elongated felt F isformed into the shape of a belt, so that the loops L at its ends can bebrought together and connected.

As shown in FIG. 2, the felt F comprises a ground fabric B and battfiber layers W formed on the obverse and reverse sides thereof. The battlayers W are formed by web fibers laminated onto the ground fabric B byintertwining integration utilizing needle punching.

The ground fabric B is a woven fabric made up of yarns extending alongthe “machine direction” (MD), i.e., the direction of belt movement, andyarns extending along the “cross-machine direction” (CD). The seam loopsL are formed by yarns extending along the MD direction.

When installed in a papermaking machine, and before its ends areconnected together, the felt is hung on the machine and both ends of thefelt are brought into abutment with each other. Then, the loops at therespective ends of the felt are intermeshed in an alternatingarrangement so that, except at the ends of the rows of seam loops in theCD direction, each loop on one end of the felt is disposed between twoadjacent loops on the other end of the felt.

As shown in FIG. 2( a), when the meshing operation takes place theportions of the felt near its ends are not in parallel, coplanarrelationship. Instead, the two ends are arranged to form a peak, andthen the loops are brought into intermeshing relationship. In otherwords, when the loops are brought into intermeshing relationship, loopsat one end of the felt are moved upward into spaces between adjacentloops at the other end in a direction transverse to the direction inwhich the latter loops extend from their end of the felt. In practice, ajig (not described) is usually employed to facilitate the intermeshingof the seam loops.

After the loops are brought into intermeshing relationship, as shown inFIG. 2( b), the loops of both ends of the felt form a common bore intowhich a seam thread S is inserted. Thereafter, the ends of the felt, nowconnected but still forming a peak, are brought into coplanarrelationship to complete the formation of the endless papermanufacturing felt known as a “seam felt.”

Because they can be installed easily in a papermaking machine, the useof seam felts has recently increased as explained in Japanese Laid-OpenPatent application No. 2004-232142.

When the felt F is converted from a configuration having two free endsto an endless configuration, the opposite sides of the belt constitutean outer circumferential side and an inner circumferential side,respectively. The outer circumferential side contacts a wet paper web,and the inner circumferential side comes into contact with a press roll.

The structure of the ground fabric B is shown schematically in FIG. 3,which illustrates a double woven ground fabric at one end of the belt.The yarns extending in the MD direction are turned back on themselves sothat each yarn includes upper side and lower side elements.

The ground fabric B comprises MD yarns 11A to 14B, and CD yarns 21 to24. In the group of MD yarns 11A to 14B, yarns 11A and 11B arecontinuous with each other, as are yarns 12A and 12B, 13A and 13B, and14A and 14B. Seam loops L are formed at each end of the ground fabric byvirtue of the fact that the MD yarns are turned back on themselves.

To stabilize the forms of the seam loops, heat setting is performed in anext manufacturing step. Thereafter, the seam loops at both ends of theground fabric B are intermeshed with one another and the ends of theground fabric are connected by insertion of a seam thread S though theintermeshed loops. Batt fiber layers are then intertwiningly integratedwith the ground fabric in a needle punching step. The completed felt isshown in FIG. 4 (see U.S. Pat. No. 4,938,269). In FIG. 4, the seam loopsof one end are shown somewhat darker than the seam loops at the otherend so that it is more easily seen that the seam loops are meshed in analternating arrangement.

When the seam felt is completed, the seam thread S is pulled out, andthe seam loops become disengaged so that the felt again has two freeends. The felt can then be packaged for shipment. When the felt is newlyinstalled in a papermaking machine, the rolls of the machine do not needto be dismounted and their supports do not need to be disengaged. Theseam felt which is to be newly installed is brought into the papermachine with the aid of a guiding as described in Japanese Laid-OpenPatent Application No. 284092/1996.

When the new seam felt is in place on the machine rolls, its free endsare brought into abutment with each other, and a seam thread S isinserted into the tubular space formed by the intermeshed seam loops Lof the opposing ends of the felt. If the meshing of the seam loops L ispoor, the insertion of the seam thread S can require a considerableamount of time and effort. For example, if a loop becomes slanted, or isdrawn into the ends of the felt along the MD direction, the insidediameter of the loop can become smaller. When one or more of the loopsbecomes smaller, the space for receiving the seam thread S, formed bythe intermeshing loops, becomes uneven, increasing the difficulty ofinsertion of the core line member.

In addition, the engagement of the seam loops L in an alternatingarrangement is by its nature complicated and difficult. The difficultyof arranging the loops in proper intermeshing relationship alsoincreases as the diameter of the MD direction yarns decreases, makingthe assembly of the felt more time-consuming.

SUMMARY OF THE INVENTION

An object of the invention is to solve the above-mentioned problems, andto provide a seam felt for paper manufacture having ends that can bejoined more quickly and easily so that installation of the felt in apapermaking machine can be carried out more quickly and easily.

I have discovered that forming groups of seam loops, each with two ormore yarns in the MD direction arranged in side by side relationshipleads to a solution of the above-described problems.

The seam felt for paper manufacture according to the invention has somefeatures in common with a conventional seam felt. These features includethe fact that it comprises a ground fabric having two ends meeting eachother so that the felt forms a closed loop, the direction around theloop being a machine direction, and each of the ends being formed withseam loops intermeshed with seam loops formed at the other end andforming a common bore, a seam thread S extending through the common boreformed by the intermeshed seam loops, thereby connecting said ends ofthe fabric together, and batt fiber layers intertwiningly integratedwith the ground fabric by needle punching.

In the seam felt according to the invention, however, the intermeshedseam loops comprise groups of seam loops formed on each of the ends ofthe belt. The groups of seam loops formed on the respective ends of theground fabric are intermeshed with one another in alternatingrelationship, and each said group is composed of a plurality of seamloops on the same end of the ground fabric arranged in side by siderelationship without seam loops formed on the other end of the groundfabric interposed between any of the seam loops of said group.

Preferably, each group of seam loops is composed of at least two but notmore than three seam loops.

In an embodiment of the invention, the seam loops forming each group areintegrated with one another by adhesive bonding.

In an alternative embodiment, yarns of the seam loops, which are yarnsof the ground fabric extending in the machine direction, are eachcomposed of a core-in-sheath composite fiber comprising a sheathsurrounding a core. The melting temperature of the sheath is lower thanthe melting point of the core, and the seam loops in each of the groupsare integrated by fusion of their sheaths, that is, by heat adhesion.

Preferably, the distance between adjacent seam loops in a group is equalto or smaller than the diameter of the MD yarns of the ground fabric.Even more preferably, the seam loops are formed such that adjacent seamloop within a group are in contact with each other or almost in contact

One of the advantages of the Invention is that, with groups of seamloops each composed of two or more loops of MD yarn arranged side byside, even if the yarns forming the seam loops are thin, the seam loopsat the opposite ends of the ground fabric can be brought easily intostable meshing relationship easily when the ends are connected while thefelt is being installed in a papermaking machine.

Another advantage is that if the seam loops in a group are joinedtogether by adhesive bonding or fused together, the group becomes moredifficult to displace either in the cross-machine direction or indirections transverse to the faces of the felt. Therefore, the seamloops can be more stably positioned in the desired configuration so thatintermeshing of the seam loops can be carried out smoothly.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view of a conventional felt for papermanufacture, in which the ends of the felt are separated from eachother;

FIGS. 2( a) and 2(b) are respectively sectional and perspective views,illustrating the meshing of the ends of the felt of FIG. 1;

FIG. 3 is a fragmentary perspective view showing details of the seamloop part of the conventional felt;

FIG. 4 is a schematic perspective view of the conventional felt showingthe completion of the connection of its ends;

FIG. 5 is fragmentary perspective view of the seam loop part of a feltaccording to the invention;

FIG. 6 is a sectional view along the CD (cross direction) direction of afelt for paper manufacture according to a different embodiment of theinvention; and

FIG. 7 is a perspective view illustrating the meshing state of the seamloop part of a felt according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 5 shows one end of a double weave ground fabric BA according to theinvention. The ground fabric BA is a woven fabric comprising MD yarns 50and CD yarns 60. The MD yarns 50 are turned back on themselves at anend, and arranged in groups LA1, LA2 . . . LAn, each group beingcomposed of two seam loops in side-by-side relationship. As shown inFIG. 5, the seam loops in each group are in contact or almost in contactwith each other. The seam loops in each group can be disposed either incontact with each other or spaced from each other by an interval equalto or smaller than the fiber diameter of the MD yarns 50.

The MD yarns 50 are preferably supplied to the weaving machine asmonofilament yarns. Preferably, each group of seam loops is composed oftwo or three monofilament yarns. If a group of adjacent seam loops iscomposed of four or more yarns, the distance between groups of seamloops, i.e., a distance corresponding to the distance between groups LA1and LA2 in FIG. 5, will become excessively wide, impairing the strengthof the seam and bringing about a risk of seam failure.

The CD yarns 60 can be either single monofilament yarns or twistedmonofilament yarns. Multifilament yarns or spinning yarns are preferablyemployed as the CD yarns 60 a in the vicinity of the seam thread S, sothat the intertwining of the batt fibers with the CD yarns by needlepunching is strengthened at and near the locations of the seam.

After the ground fabric BA is prepared by weaving, it is heat set inorder to stabilize the forms of the seam loops. With the groups of seamloops at both ends of the ground fabric intermeshed in alternatingrelationship the ends of the ground fabric are connected by insertion ofa seam thread S, batt fiber layers are intertwiningly integrated withthe ground fabric by needle punching to complete the felt.

The seam thread S is pulled out of the seam loops of the completed feltto disengage the ends of the felt. The product can then be packaged forshipment. In the same manner as in the case of a conventional felt, theseam felt according to the invention is mounted on to a papermakingmachine. Then, with both ends of the seam felt in abutment with eachother and with a plurality of groups of seam loops at both ends in meshwith one other in an alternating arrangement, a seam thread S isinserted into a common bore formed by the meshing of the seam loops toconnect the ends of the seam felt together, forming an endless seam felton the papermaking machine.

It is desirable to join the seam loops of each group together using anadhesive so that they are integrated with each other. Alternatively,where the MD yarns are core-in-sheath composite fibers in which thesheath has a lower melting point than that of the core, the seam loopsof each group can be joined, and thereby stabilized, by heat adhesion,causing the sheaths to fuse to one another. The joining of the seamloops for stabilization of the loops by heat can be carried out in aheat setting process.

A group of seam loops may consist of more than two seam loops arrangedside by side, so that, even if the MD yarns forming the seam loops arethin, the seam loops at the opposite ends of the felt can be meshedeasily and stably when seaming is carried out on a papermaking machine.In addition, if the seam loops in a group are bonded together, the groupis less easily displaced in the cross machine direction and also lesseasily displaced in directions transverse to the faces of the felt. Whenthe seam loops of the groups are bonded together, the seam loops can bestably positioned and their configuration maintained so that meshing canbe carried out smoothly.

With the seam loops in groups, and especially when the seam loops ineach group are bonded together, it is less likely that loops willbecomes slanted, or drawn into the ends of the felt along the MDdirection so that their inside diameters become smaller. Therefore thecommon bore formed by the meshed loops can be more uniform, and the seamthread S can be inserted easily.

Examples of seam felts in accordance with the invention will now bedescribed by way of illustration but not for the purpose of limiting thescope of the invention. For the examples, the following yarns wereprepared for use as MD yarns and CD yarns:

-   -   Yarn A: monofilament (single yarn) of nylon 6.    -   Fineness: 1000 dtex (diameter of fiber: 0.33 mm)    -   Yarn B: monofilament (single yarn) of nylon 6.    -   Fineness: 500 dtex (diameter of fiber: 0.23 mm)    -   Yarn C: monofilament (single yarn) of core-in-sheath composite        fiber having nylon 6, with a high melting point of 250 degrees        Celsius, as the core, and copolymerized nylon, with a lower        melting point of 180 degrees Celsius, as the sheath.    -   Fineness 1000 dtex (diameter of fiber: 0.32 mm)

Example 1

In this example, yarn A was employed as the MD yarns, and yarn B wasused as the CD yarns. The ground fabric BA1 was fabricated by 3/1 1/3warp double weaving. A cross-sectional view of the weave in the CDdirection is shown in FIG. 6. For the MD yarns, two yarns set side byside were supplied to the weaving machine so that the seam loops areformed with two yarns constituting one group. For the ground fabric BA1,the MD yarns were turned back on themselves at the position of the seamthread S as shown in FIG. 7.

FIG. 7 is a perspective view of the seaming section of the ground fabricBA1 showing groups LB1 and LA2 of seam loops at one end, and a groupsLB1 at the other end, joined together by a seam thread S form andendless felt.

Following weaving, the ground fabric BA1 was drawn out from the weavingmachine, and hung on a pair of rolls. Then, the ground fabric wassubjected to heat treatment, using a heating device (not shown). Theheating device can be installed on one of the rolls or between therolls. The heat treatment heat sets the ground fabric BA1, stabilizingthe forms of the seam loop groups. Afterward heat treatment, a liquidresin was applied to the seam loop groups and dried. The application anddrying of the resin bonded the seam loops of each group, integratingthem together. Where the seam thread S is constituted by a yarn made ofresin having low surface free energy, such as a fluoric resin, theliquid resin may be applied only to a part of the groups of seam loops,making it easier to draw out the seam thread S.

Following heat treatment and resin application, the ground fabric BA1was hung onto a needle punching machine, and laminated with batt fiberscomprising 15 dtex staple fibers. The needle punching operationintertwines the batt fibers with the ground fabric, integrating thelayers to complete the seam felt. The batt fiber layers were laminatedwith a basis weight of 300 g/m² on the outer circumferential side of thefelt, and with a basis weight of 100 g/m² on the inner circumferentialside.

As a final step, the seam thread S was pulled out of the felt, so thatthe completed seam felt 1 in accordance with the invention had two freeends.

Example 2

As in the first example, in this example, yarn A was employed as the MDyarn, and yarn B was used as the CD yarn. The ground fabric was woven in3/1 1/3 warp double weave.

In this case, the supply speed of the CD yarn and the supply speed ofthe MD yarn were adjusted on the weaving machine so that the seam loopsof each group were separated by a distance close to the diameter of yarnA. A ground fabric having a 0.2 mm seam loop interval in the seam loopgroups was obtained. The remaining conditions were the same as inExample 1. Thus, the seam felt 2 of the present invention was completed.

Example 3

In this example, yarn C was used as the MD yarn, and yarn B was employedas the CD yarn, the ground fabric was prepared in he same manner as thatin Example 1. The ground fabric was then subjected to heat setting, asin example 1, to stabilize the forms of the groups of seam loops. Inthis example, the heat set temperature was adjusted to at least 180degrees Celsius, causing the copolymerized nylon sheath of the yarn C tomelt, thereby joining the seam loops of each group. In other respects,the process was the same as in Example 1. Thus, the seam felt 3 of thepresent invention was completed.

Example 4

In this example, yarn A was used as the MD yarn, and yarn B was used asthe CD yarn. For the MD yarn, three yarns were supplied as one set tothe weaving machine, so that each seam loop group was composed of threeyarns. In other respects, the example (seam felt 4) was the same asExample 1.

Example 5

In this example, yarn A was used as the MD yarn, and yarn B used as theCD yarn. For the MD yarn, four yarns were supplied to the weavingmachine as one set, and consequently each group of seam loops wasconstituted by four yarns. In other respects, the conditions were thesame as those of Example 1. Thus, the seam felt 5 of the presentinvention was completed.

Comparative Example 6

In a comparative example (seam felt 6), yarn A was used as the MD yarn,and yarn B was as the CD yarn. The yarns were woven in a 3/1 1/3 warpdouble configuration to produce a ground fabric B. The MD yarn wascomposed of only one continuous yarn and the MD yarns were turned backat one end. As shown in FIG. 3, each seam loop was composed of only asingle yarn having top and bottom elements. The manufacturing processwas otherwise the same as that of Example 1.

The seam strength, the conditions of meshing, and the ease of mountingof the seam felts made according to the six examples were determined.The results are shown in Table 1 below.

Seam strength was evaluated, in units of kg/5 cm, by the cuttingstrength when the seam thread was interposed in the common bore definedby the meshed seem loops.

In the evaluation of meshing conditions, the degree of inclination ofthe seam loops, and the degree to which the seam loops were drawn intheir root direction into the felt were examined. When the total numberof inclined groups of loops and drawn-in loops in a seam section 1 m inlength was less than five, the seam was evaluated as “good”; when therewere five or more but no more than ten inclined groups and drawn-inloops, the seam was evaluated as “slightly good”; and when there weremore than ten inclined groups of loops and drawn-in loops, the seam wasevaluated as “poor”.

The ease of mounting was evaluated on the basis of the time in workinghours needed for seaming per 1 m in the CD direction after the seam feltwas mounted onto a papermaking machine.

TABLE 1 meshing condition ease of felt seam felt seam strength of seamloop mounting work seam felt 1 200 slightly good 3 seam felt 2 200slightly good 3 seam felt 3 200 good 3 seam felt 4 180 good 1 or lessseam felt 5 150 good 1 or less seam felt 6 200 poor 5 or more

The numbers assigned to the seam felts in column 1 correspond to theexample numbers. When the seam strength of seam felt 1 is compared withthat of seam felt 6 (the comparative example) no difference was found toexist. In seam felt 1, there is an interval of two MD yarn widthsbetween the groups of the seam loops, but, with this interval, there isno noticeable influence on the strength of the seam. The meshingcondition was evaluated as “slightly good” and the ease of mounting wasbetter than the ease of mounting of seam felt 6. Seam felt 2, in whichthe seam loops of each group do not come into direct contact but areseparated by a small interval achieved an evaluation equivalent to theevaluation of seam felt 1.

The seam felt 3, in which a core-in-sheath composite fiber was employedas the MD yarn, achieved a better meshing condition evaluation than thatachieved by seam felt 1, where a liquid resin was applied to harden theneighborhood of the seam loops.

Seam felt 4 exhibited a slightly lower seam strength, but good meshingconditions, and superior ease of mounting.

Finally, in the case of seam felt 5 where each group of seam loopsconsisted of four yarns, the interval between groups of seam loops wasequal to four MD yarn widths. This resulted in a slight drop off of seamstrength compared to that of seam felt 4. However, meshing conditionswere good, and ease of mounting was very good, as in the case of seamfelt 4.

It should be understood that the examples described herein are not theonly possible embodiments of the invention. Other embodiments will beapparent to persons skilled in the art from the foregoing description,and are within the scope of the invention as defined by the followingclaims.

1. A seam felt for paper manufacture comprising a ground fabric having two ends meeting each other so that the felt forms a closed loop, the direction around the loop being a machine direction, and each of said ends being formed with seam loops intermeshed with seam loops formed at the other of said ends and forming a common bore, a seam thread extending through said common bore formed by the intermeshed seam loops, thereby connecting said ends of the fabric together, and batt fiber layers intertwiningly integrated with said ground fabric by needle punching, wherein the intermeshed seam loops comprise groups of seam loops formed on each of said ends, said groups formed on the respective ends of the ground fabric being intermeshed with one another in alternating relationship, and wherein each said group is composed of a plurality of seam loops on the same end of the ground fabric arranged in side by side relationship without seam loops formed on the other end of the ground fabric interposed between any of the seam loops of said group.
 2. A seam felt for paper manufacture according to claim 1, wherein each said group of seam loops is composed of at least two but not more than three seam loops.
 3. A seam felt for paper manufacture according to claim 1, wherein the seam loops forming each said group are integrated by adhesive bonding.
 4. A seam felt for paper manufacture according to claim 1, wherein the seam loops are formed by yarns of the ground fabric extending in the machine direction, each said yarn being a core-in-sheath composite fiber comprising sheath surrounding a core, wherein the melting temperature of the sheath is lower than the melting point of the core, and wherein the seam loops in each of said groups are integrated by fusion of their sheaths.
 5. A seam felt for paper manufacture according to claim 1, wherein each said group of seam loops is composed of at least two but not more than three seam loops, and wherein the seam loops forming each said group are integrated by adhesive bonding.
 6. A seam felt for paper manufacture according to claim 1, wherein each said group of seam loops is composed of at least two but not more than three seam loops, and wherein the seam loops are formed by yarns of the ground fabric extending in the machine direction, each said yarn being a core-in-sheath composite fiber comprising sheath surrounding a core, wherein the melting temperature of the sheath is lower than the melting point of the core, and wherein the seam loops in each of said groups are integrated by fusion of their sheaths. 